The life expectancy of wheel constructions, particularly the type adapted for use with a yoke assembly, is continuously being subjected to review. Generally, it can be stated that the failure of such a wheel construction is primarily due to a failure in the ball-bearing assembly. My U.S. Pat. No. 3 807 817 represents a unique bearing assembly which has substantially prolonged the life of wheel constructions. In addition, such bearing assembly has reduced the cost of the total wheel construction.
The bearing assembly illustrated in my aforementioned U.S. Pat. No. 3 807 817 is a type wherein the axle and the sleeve having the bearings located therebetween are preassembled. However, a problem has existed in assembling the preassembled bearing construction into a wheel and having the axis of the bearing construction end up concentric with the outer diameter of the wheel. In addition, a problem continues to exist in protecting the bearing assembly from shock loads which are, from time to time, applied to the support construction, particularly the yoke. It is well known that the life of a bearing, hence of the wheel upon which it is mounted, is materially affected by the amount of looseness or play in the bearing parts thereof. Thus, where bearing parts are assembled with an excess amount of initial play, the useful life of the bearing is shortened in a corresponding manner. That is, unnecessary runout, radial play or axial play in the bearing parts relative to each other, or in the bearing parts relative to the wheel which they support, will tend to induce or accelerate wear which merely increases the play. In a sense, this results from the fact that the loose parts have an opportunity to hammer each other during normal use of the wheel or other structure in which the loose bearing is used. This acceleration in deterioration of loose bearing assemblies is especially noticeable in situations of severe usage, such as in the wheels of castors.
Furthermore, it has been largely taken for granted that looseness or excess play had to be tolerated in return for low cost bearing constructions. Accordingly, it is not uncommon for certain users, such as owners of supermarket shopping carts, to accept bearing failures in a relatively short period of time due to severe shock loading that can occur during normal use thereof. It is a desire, therefore, of this invention to provide a wheel construction utilizing a bearing assembly which has successfully overcome the problem of developing looseness during use thereof in a wheel and assuring that the outer diameter of the wheel is concentric with the axis of the bearing assembly. In addition, it is desirable to provide a wheel construction wherein the shock loads applied to the wheel construction are isolated from the bearing assembly.
Accordingly, it is an object of this invention to provide a wheel construction wherein the axis of the bearing assembly is assured of being concentric with the outer diameter of the wheel.
A further object of the invention is to provide a wheel construction, as aforesaid, which is particularly adaptable for use in the wheels of a castor or the like where the treatment received by the bearing assembly, even under normal conditions of use, is severe by any reasonable standard.
A further object of this invention is to provide a wheel construction, as aforesaid, having a sufficient structural simplicity that it can be assembled rapidly, accurately and inexpensively.
A further object of the invention is to provide a wheel construction, as aforesaid, comprised of a minimum number of parts, each part being of such structural configuration that it is capable of being assembled so that the strength of the assembly is increased during the assembly.
A further object of the invention is to provide a wheel construction, as aforesaid, in which the bearing assembly can be constructed in a variety of sizes and for a variety of specific uses with a minimum of modifications and structural limitations.
A further object of the invention is to provide a wheel construction, as aforesaid, wherein the full effect of shock loads or the like applied to the wheel construction are isolated from the bearing construction.